Similar to Aquinas’s angels, Tolkien makes clear that the embodiment of the Valar is not something natural to them, as is the case with Men and Elves, but is undertaken voluntarily so that they are able to go without their bodies should they wish or the need arise. Tolkien writes of the Valar in one letter: “They were thus in the world, but not of a kind whose essential nature is to be physically incarnate. They were self-incarnated, if they wished; but their incarnate forms were more analogous to our clothes than to our bodies, except that they were more than are [sic] clothes the expression of their desires, moods, wills and functions” (Letters 259; see also 235, 284-5, and 411). And in the Ainulindalë, their incarnation is put this wise:
“Now the Valar took to themselves shape and hue; and because they were drawn into the World by love of the Children of Ilúvatar, for whom they hoped, they took shape after that manner which they had behold in the Vision of Ilúvatar, save only in majesty and splendour. Moreover their shape comes of their knowledge of the visible World, rather than of the World itself; and they need it not, save only as we use raiment, and yet we may be naked and suffer no loss of our being. Therefore the Valar may walk, if they will, unclad, and then even the Eldar cannot clearly perceive them, though they be present. But when they desire to clothe themselves the Valar take upon them forms some as of male and some as of female; for that difference of temper they had even from the beginning, and it is but bodied forth in the choice of each, not made by the choice, even as with us male and female may be shown by the raiment but is not made thereby.” (S 24)
There is also indication that, again like Thomas’s angels, it is because the Valar are especially concerned with the Children of Ilúvatar that the bodies they assume are of human shape. Furthermore, because the angelic spirit is united to its body not by nature but by will, the formation of its body is itself a kind of sub-creative act. Describing the angelic body, Tolkien writes: “It is mythologically supposed that when this shape was ‘real’, that is a physical actuality in the physical world and not a vision transferred from mind to mind, it took some time to build up. It was then destructible like other physical organisms” (L 260). Tolkien further explains that, when an angelic spirit’s body was destroyed (as happens twice, for example, in Sauron’s case), each time it would take longer for the spirit to re-fashion its body: “because each building-up used up some of the inherent energy of the spirit, which might be called the ‘will’ or the effective link between the indestructible mind and being and the realization of its imagination” (L 260). As in Thomas’s angelology, Tolkien’s angelic beings are not able to make matter obey instantaneously or effortlessly the dictates of their will, but are only able to form their own and other bodies through a true sub-creative effort, one involving the passage of time and an apparently un-renewable expenditure of great personal energy and vitality.